"degree" curves

[BigBoy4023]

I was watching a video about the West Side Lumber Company, and 60º curves are mentioned in terms of sharpness of the curve, and not the angle of a circle that they complete... How is that translated into an actual radius? I believe the quote was "as sharp as 60º" Thanks

[rrinker]

 You need to know a little geometry, or civil engineering. When we build amodel railroad, we can usually just mark of the curve radius from the center point. Not so easy for the real thing, unless you are 4 mile tall giant. So surveyors mark off curves in degrees per a certain chord length - typically 100 feet. It's usually not a big deal to mark off 100 feet, then using a transit sight off in the desired direction by a certain number of degrees.

 This site explains it all in detail: http://mysite.du.edu/~jcalvert/railway/degcurv.htm

                              --Randy

[dehusman]

The degree of curvature is the angle subtended by a 100 foot chord.

On many class one railroads typical curves are the 1-5 degree range and 10 degree or above is considered "sharp".

Radius = 50/sin a (where a = one half the degree of curvature in degrees)

So a 60 degree curve would be a 100 ft radius (a 2 degree curve is  2864 ft radius and 10 degree curve is 573 ft radius).

 

[cuyama]

dehusman

So a 60 degree curve would be a 100 ft radius

Or just over 13 3/4" in HO.

[BigBoy4023]

Thanks everyone!

[markpierce]

here is a conversion table

http://www.urbaneagle.com/data/deg-curve.txt

 

[johncolley]

Railroad curves were determined by sighting along the line, moving the transit the desired angle, andmeasuring a surveyor's chain of 100 feet. The radius of a 1 degree curve is 5729 feet. the radius of any curve can then be determined by dividing 5729 by the desired angle of curvature. It must be noted that this is not the same as the total deflection angle between two tangent tracks. Most mainline curves are in the 1 to 5 degree range to allow them to be taken at track speed. In mountain areas or to follow a river course they might go up to 10 degree curves, often with speed restrictions. Industrial site curves, depending on the railroad and local conditions might be restricted to 12.5 degrees unless special situations require an even tighter radius. John